Power supplies such as welding power supplies are used to provide high amperage current. Typically, in a welding power supply, a pair of output terminals is provided. A welding cable connected to the welding torch (or stinger, drive assembly or welding circuit) is inserted into one of the two output terminals. The other output terminal receives a welding cable which is connected to the workpiece being welded. Typically, the connectors are twist lock type connectors (also called international connectors), the power supply has a female connector, and the welding cable has a mating male connector. In some designs the cable has a female connector and the power supply a male connector.
One prior art twist lock connector is shown in FIGS. 1-3. The prior art connector, as shown in FIG. 3, includes a twist lock receptacle 101, a front bulkhead insulator 102, a rear bulkhead insulator 103, a lock washer 104, a nut 105, a washer 106, a lock washer 107 and a hex bolt 108. Hex bolt 108 and washers 104, 106 and 107 are comprised of zinc plated steel, and twist lock connector 101 and nut 105 are comprised of brass. The front and rear bulkhead insulators, 102 and 103 are phenolic. The steel and brass components are used to provide for adequate electrical contact. A phenolic is typically used because it is a good insulator, flame-retardant, and will not melt.
Referring now to FIG. 1, a view of the prior art connector from outside the power supply is provided. Front bulkhead insulator 102 includes a ridge, as depicted by the concentric circles of FIG. 1. The inner perimeter of front bulkhead insulator 102 is hexagonal in shape. A twist lock receptacle 101 has a hexagonal outer perimeter and fits tightly within front bulkhead insulator 102. Twist lock receptacle 101 includes a circular opening 116 having an axial notch 115. A circumferential, slightly helical, notch 117, within twist lock receptacle 101, may be seen in FIGS. 2 and 3. When the welding cable is connected, a key on the male connector attached to the welding cable mates with notch 115, and when the cable connector has been inserted all of the way, the cable connector is rotated and the key turns in circumferential notch 117. The male connector is pulled tightly to the face of the female connector by the action of the helical-shaped notch. Thus, the cable connector is locked into place and the desired electrical contact is obtained.
Referring now to FIG. 2, front bulkhead insulator 102 is inserted into a hole in a power supply chassis 112. The hole in power supply chassis 112 includes a notch which receives a key 119 on front bulkhead insulator 102. Thus, front bulkhead insulator 102 does not twist when the male connector on the welding cable is being rotated to lock it into place.
An end 120 of twist lock receptacle 101 extends within the welding power supply and rear bulkhead insulator 103 is mounted thereon. Rear bulkhead insulator 103 and front bulkhead insulator 102 are designed to mate and welding power supply chassis 112 is sandwiched between them. Also, the notch on front bulkhead insulator 102 is received in a similarly and oppositely notched portion 122 of rear bulkhead insulator 103, to prevent the inner portion of the connector from rotating.
Inner end 120 of twist lock receptacle 101 is threaded and nut 105 has mating threads to allow nut 105 to be threadedly mounted on twist lock receptacle 101. Thus, nut 105 and lock washer 104 are used to maintain contact between front bulkhead insulator 102, welding power supply chassis 112 and rear bulkhead insulator 103.
End 120 of twist lock receptacle 101 is hollow, and its inner surface is threaded. The threaded interior portion receives hex bolt 108, about which washer 106 and lock washer 107 are disposed. As shown in FIG. 2, an internal electrical connection 110 is placed between the inner end of twist lock receptacle 101 and washer 106. The internal electrical connection 110 may be a copper lug, an aluminum bus bar, or any other internal electrical connection. Some prior art connectors include a gas fitting that replaces hex bolt 108, and an O ring disposed within twist lock receptacle 101 near notch 117 that seals the gas flow path (through the connector and into the cable).
Thus, it may be seen that the prior art connectors provided for a secure and locking electrical connection between an internal electrical connection and the welding cable.
It is not unusual for welding power supplies to be used outside, for example at construction sites. Thus, they are often exposed to rain or may otherwise get wet. Also, to obtain IEC certification (or other certifications such as UL, CSA, NEMA etc.), welding power supplies must be subjected to a "rain test". In such a test, the power supply will be subjected to water, to ensure that premature failures in the field will not occur.
However, in the prior art connectors water sometimes seeps between front bulkhead insulator 102 and welding chassis 112. The water then seeps down between front bulkhead insulator 102 and rear bulkhead insulator 103. The potential water leakage path is labelled 118, and is shown as a solid black line. As water leaks in along path 118, it may provide a conductive path from twist lock receptacle 101, which is electrically hot, to chassis 112, which should be grounded. Thus, this path may provide an undesirable short.
It is typical to provide a welding power supply with a high frequency arc starter. A high frequency arc starter provides a low current, but high voltage, high frequency signal. Such a high voltage signal can arc along path 118 from twist lock receptacle 101 to welding power supply chassis 112. This problem is exacerbated when water seeps into path 118.
One prior art attempt to solve the problems of water leakage and high frequency arcing is to apply a RTV (room temperature vulcanizing) compound in an attempt to seal path 118. However, such a compound is difficult to apply and does not adequately solve the problem. Additionally, a second potential water seepage path 118A may be found between twist lock receptacle 101 and front bulkhead insulator 102.
Accordingly, it is desirable to provide a power supply connector that will reduce the likelihood of water leaking into the power supply and causing a short therein, or to have a short during high frequency arc starting. Such a connector should preferably be a locking cable receptacle, with an anti-rotational fitting and relatively simple and easy to manufacture.